Aga Khan Development Network in Tajikistan were using the Mountain High EDS portable O2 system when I was there a few years back. Bottle was strapped to the back of the pilots seat. With Mountain High, you can get distribution boxes that will allow a couple of cannulas or masks to be used off of one bottle. Have a look at the Mountain High website:
Mountain High Aviation Oxygen Systems
And because they are pulse/demand systems instead of constant flow, you get more duration out of your bottle. I've used them alot gliding. Cannulas aren't certified above 18000 feet in most countries though, so I carry a mask as well.
Hope that points you in the right direction.